The Scottish Government has published a written request from DUP leader Arlene Foster asking that it restrict gay couples from Northern Ireland converting their civil partnerships to same sex marriages in Scotland.
The publication comes days after Mrs Foster said she had no recollection of sending such correspondence to the administration in Edinburgh.
The letter, written in September 2015 when Mrs Foster was Stormont finance minister, urged then Scottish local government minister Marco Biagi to exclude Northern Ireland-based couples from legislation that enabled people in civil partnerships to convert those unions to same sex marriages.
Mr Biagi tweeted about the existence of the letter in the wake of the General Election, amid increased UK-wide focus on the DUP's conservative stance on social issues such as gay marriage.
But in a radio interview last week, the former Stormont first minister denied sending such a letter.
"I'm not quite sure what he (Mr Biagi) was referring to but it certainly wasn't a letter from me and I've no recollection of a letter from me," she told BBC Radio Ulster's Inside Politics show.
"If I'd written to him officially as minister of finance or something like that around recognition laws here in Northern Ireland, I have no recollection of it. I certainly didn't write in a personal capacity."
The letter dated September 4 2015 released by the Scottish Government on Tuesday is signed by Mrs Foster.
It was a follow-up to a letter from her predecessor as finance minister, the DUP's Simon Hamilton. Mr Hamilton's letter has also been made public.
The letters did not cite moral or political objections to the proposed legislation in Scotland, but highlighted potential legal issues.
They said complications could arise from couples having "dual status", where they are recognised as civil partners in Northern Ireland but as married in Scotland.
Mrs Foster wrote: "I'm sure neither of us would wish to place same sex couple in an uncertain legal position, which maybe difficult and expensive to resolve."
Mr Biagi rejected the request from the Northern Ireland ministers.
In his reply to Mrs Foster, dated November 24 2015, he said it would "not be appropriate" to exclude Northern Ireland couples from availing of the legislation.
Stormont's department of finance has responsibility for marriage regulations in Northern Ireland.
In response to the publication, a DUP spokesman said: "This correspondence was exploring technical legal matters and was not personally driven by the minister.
"Marriage legislation is a fully devolved matter for the Northern Ireland Assembly."
I said no.— Marco Biagi (@MarcoGBiagi) June 10, 2017